Do I Believe that Xavier's Actions in Dying are Justified?

In the chapter Justified of Three Day Road, Xavier, after a long period of mentally struggling in a sense against his friend Elijah, has to make a hard decision. As they attempt to take a fortified line, their squad is slowly cut down by machine guns. Elijah, the highest ranking soldier, takes command of the squad, and orders the rest to provide covering fire for himself and Xavier and then retreat. Xavier immediately sees trouble in the near future, and as two heavy bombardments rage around them, they pick off Germans until Elijah turns to him, states while smiling that he "has gone too far" and then proceed to viciously attack and almost kill Xavier. Xavier, at this point is forced to kill him by choking him to death. This, I feel is justified seeing as it was self-defence, and though it may have been scarring, Xavier can at least know that he was forced to kill his best friend by circumstance, not choice.